Response surface optimization of glucose production from liquid pineapple waste using immobilized invertase in PVA–alginate–sulfate beads

• A Box–Behnken design was used in glucose production.
• The glucose production was done by immobilized invertase.
• PVA–alginate–sulfate beads was used as the immobilization matrix.
• The optimum condition was studied.
• Overall glucose generated was approximately 1131% of its original content.

Pineapple waste is known as a byproduct of the pineapple processing industry and typically consists of residual pulp, peels and skin. In this study, the conversion of sucrose to glucose was performed with the help of Baker’s yeast invertase. Response Surface Methodology (RSM) comprising Box–Behnken design was successfully applied in this study as a tool to evaluate the interactive effects and to obtain the optimum operating conditions for the enzymatic hydrolysis. Four parameters were varied: pH (4–6), temperature (40–60 °C), agitation rate (100–200 rpm) and amount of immobilized beads (3–6 g). Results revealed that the optimum operating conditions derived via RSM were: pH 4.74, temperature 50.11 °C, agitation rate of 147.68 rpm and amount of immobilized beads used were 4.45 g. The experimental yield of glucose was found to be 111.42 g/L (850.5%) and sucrose 25.70 g/L (32.3%) under the optimum conditions, which correlated well with the maximum predicted value of glucose and sucrose 110.13 g/L (840.7%) and 25.93 g/L (32.6%) respectively. Hydrolysis of the liquid pineapple waste showed that 95% of sucrose content in the waste was hydrolyzed to glucose after 3 h of hydrolysis and the overall glucose generated from the hydrolysis was approximately 1131% of its original content.